1. Field of the Invention
The present invention relates to the monitoring of audio content, and more specifically to systems and methods for automatically identifying audio content that is broadcast.
2. Description of Related Art
Copyrighted audio content such as music is broadcast to listeners over various mediums that include radio, television, cable television, satellite television, and Internet web sites. Each time a copyrighted song is broadcast, a performance royalty is due to the holders of the performance rights in the song (e.g., the songwriter and music publisher). Typically, each broadcaster (i.e., radio station, television network, television station, cable or satellite system, and web radio station) obtains a general license from a licensing organization such as ASCAP or BMI to broadcast a wide range of audio content. The performance royalties received for these licences is then divided between all performance rights holders (e.g., songwriters and publishers) that are members of the licensing organization based on the number of times each song is performed.
However, this assignment of royalties to individual rights holders is currently done through manual review and a very sparse sampling of broadcasts. Thus, performance royalties for less popular songs are most likely being underestimated. Further, the sparse sampling that is undertaken is at least partially based on the honor system, so the royalties received for even the most popular songs are dependent on the accuracy of the broadcasters. Thus, for copyright enforcement of performance rights, there is a need for a system and method for automatically identifying copyrighted audio content that is broadcast.
One difficulty in developing a practical system for automatically monitoring performance rights is providing a mechanism for automatically identifying audio content. One solution that has been proposed is to tag copyrighted music by using digital watermarking technology. Another solution is to identify the audio content itself. However, the identification of music even from a digital source, such as an MP3 file, is not a trivial problem. Different encoding schemes will yield a different bit stream for the same song. Even if the same encoding scheme is used to encode the same song (i.e., sound recording) and create two digital audio files, the files will not necessarily match at the bit level.
Various effects can lead to differentiation of the bit stream even though the resulting sound differences as judged by human perception are negligible. These effects include: subtle differences in the overall frequency response of the recording system, digital to analog conversion effects, acoustic environmental effects such as reverb, and slight differences in the recording start time. Further, the bit stream that results from a recording will vary depending on the type of audio source. For example, the bitstream for a song created by encoding the output of one stereo receiver will generally not match the bitstream for the same song created by encoding the output of another stereo receiver.
In addition, there are forms of noise and distortion that are quite audible to humans, but that do not impede our ability to recognize music. FM broadcasts and audio cassettes both have a lower bandwidth than CD recordings, but are still copied and enjoyed by some listeners. Likewise, many of the MP3 files on the Internet are of relatively low quality, but still proliferate and thus pose a threat to the profitability of the music industry. Furthermore, some intentional evasions of copyright protections schemes involve the intentional alteration or distortion of the music. These distortions include time-stretching and time-compressing. In such cases, not only may the start and stop times be different, but the song durations may be different as well. All such differences may be barely noticeable to humans, but can foil many conventional copyright protection schemes.
There is a need for systems and methods for automatically enforcing copyright holder rights for audio content such as sound recordings that is broadcast over a medium such as radio, television, or the Internet, such as by automatically and effectively identifying copyrighted audio content that is actually broadcast.